This invention relates to a gas-metal-arc welding process of the type which utilizes a welding gun that feeds a consumable electrode wire towards the weld deposit as the end of the wire electrode melts and is transferred to the weld deposit. A shielding gas is blown through the gun nozzle, to encircle the electrode end, the arc gap and the weld deposit.
In this type of welding process, the shielding gas is ionized by the intense electrical arc voltage to produce a plasma formation or cloud within the gap between the free end of the wire electrode and the weld deposit of molten electrode material. The plasma provides a very high degree of heat. However, in prior processes of this type involving shielding gases, the plasma tends to be relatively unstable or flickering and inconsistent. In addition, it tends to move about transversely relative to the arc axis, thus dissipating or diverting much of its heat energy away from the point at which the electrode end is melted and transferred in molten drops to weld deposit zone.
As described in my prior application Ser. No. 404,722 of Aug. 3, 1982, mentioned above, the plasma can be greatly stabilized and its heat better kept within the desired zone, by utilizing a four gas mixture comprising major proportions of each of argon and helium, and minor proportions of each of carbon dioxide and oxygen. The gas mixture within certain ranges, I have discovered, produces more effective arc control and, in particular, a stabilized or consistent, plasma.
Further, in my application Ser. No. 349,141, relating to a welding gun, I have disclosed a welding gun having a gas diverter, with passageways arranged at an acute angle relative to the axis of the gun for blowing diverging streams of the gas mixture within the gun nozzle to provide a curtain of gas exiting from the nozzle. The gas curtain shields and surrounds the electrode, the arc and the weld deposit.
This present application concerns the focusing or aiming of a substantial portion of the gas flowing from the gun nozzle which tends to form a steady, consistent arc plasma acting against transverse movement relative to, and align with the arc axis. By maintaining the plasma field centered on the arc axis, the welding zone heat is greatly intensified to produce better welds, including continuous fusion, controlled penetration, with faster welding speeds.